Xaoc Devices SARAJEWO Operator's Manual page 7

BBD
TECHNOLOGY
Bucket Brigade Delay is an
analog technology used in
vintage integrated circuits
that were popular in the 1970s,
long before digital signal converters
and digital memory were affordable. Each BBD chip contains thousands of
small capacitors and pMOS or nMOS transistors that act as analog switches. The signal is transferred as
an electric charge that is passed from one stage to the next, like a fire brigade passing buckets of water
(hence the name). A clock signal governs the speed of charge transmission, and directly controls the delay
time: the faster the clock, the shorter the delay (and vice versa). Due to the limitations of vintage technol-
ogy, signal degradation occurs—some noise and analog distortion results from the nonlinearities of MOS
transistors. Even though contemporary digital delay effects offer a much cleaner signal, BBD delays are
still sought after due to their desirable sonic characteristics. Furthermore, the range of delay time offered
by just a single BBD chip is limited to 20–300 ms, which is much less than what is commonly expected
from modern delay effects. In order to achieve more attractive delay times, several chips must be used and
the clock partially operates outside of the factory specifications. This yields additional signal degrada-
tion at extreme delay time settings due to the accumulation of noise and distortion from multiple stages.
voltage–controlled by a bipolar (±5V) signal
patched into the mix cv input.
dElAY timE VS BAndWidth
Just like any other BBD-based effect, Sarajewo
achieves long delays by reducing the clock
rate, which inevitably limits the usable band-
width. At the end of the scale, the (normally
ultrasonic) clock is slowed enough to become
an audible whine. Also, it produces some
aliasing and imaging artifacts, as well as in-
creased background noise. Sarajewo handles
this problem by automatically adjusting its
four internal filters that attenuate unwanted
components just before they become audible.
That is why the signal becomes dark when the
delay is set beyond 500ms, and even darker
the further the scale. Each unit comes factory
calibrated to achieve the optimal balance be-
tween the bandwidth and artifacts.
uSAGE tiPS
Sarajewo is intended as a long delay effect
unit, and as such, it excels at longer delay
settings. For best results at the shortest delay
settings you are advised to use the t
and combine it with moderate, but not mini-
mum delay time settings of the t
To make Sarajewo work as expected in that
configuration—and depending on the intend-
ed sonic result—you may wish to patch the t
output to the ext feedback loop input. To
mix the dry signal with the wet signal from
the t output, an external mixer is needed, as
1
the internal effect mixer always crossfades
between the dry and the t
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output
1
time dial.
3
1
signal. •
3